Various antitumor substances have been developed for use in the treatment of malignant tumors which are now the most highest cause of death.
Among these substances, cisplatin, an antitumor platinum compound, has a broad range of antitumor spectrum and takes an important role in the chemotherapy of various tumors.
However, cisplatin has a problem of causing side effects such as renal toxicity, blood toxicity, digestive organ disorder, nervous toxicity and the like. In consequence, antitumor drugs having low toxicities and high antitumor effects have been developed.
For example, antitumor effects of diamine-platinum(II) compounds represented by formula cis-[PtAA'Y.sub.2 ] (wherein A and A' are amines differing from each other and Y represents a leaving group such as a halogen atom, a carboxylate or the like) have been reported in U.S. Pat. No. 4,329,299, JP-A-60-109521 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-61-15892, JP-A-61-83194, JP-A-2-96523 and JP-A-2-4797.
These antitumor substances, however, have disadvantages in that their effects and safety are not always satisfactory and their administration by injection are limited because of their low solubility in water.